Jet Deflection via Crosswinds: Laboratory Astrophysical Studies

Abstract

We present new data from High Energy Density (HED) laboratory experiments designed to explore the interaction of a heavy hypersonic radiative jet with a cross wind. The jets are generated with the MAGPIE pulsed power machine where converging conical plasma flows are produced from a cylindrically symmetric array of inclined wires. Radiative hypersonic jets emerge from the convergence point. The cross wind is generated by ablation of a plastic foil via soft-X-rays from the plasma convergence region. Our experiments show that the jets are deflected by the action of the cross wind with the angle of deflection dependent on the proximity of the foil. Shocks within the jet beam are apparent in the data. Analysis of the data shows that the interaction of the jet and cross wind is collisional and therefore in the hydro-dynamic regime. MHD plasma code simulations of the experiments are able to recover the deflection behaviour seen in the experiments. We consider the astrophysical relevance of these experiments applying published models of jet deflection developed for AGN and YSOs. Fitting the observed jet deflections to quadratic trajectories predicted by these models allows us to recover a set of plasma parameters consistent with the data. We also present results of 3-D numerical simulations of jet deflection using a new astrophysical Adaptive Mesh Refinement code. These simulations show highly structured shocks occurring within the beam similar to what was observed in the experiments.

The hydrodynamics of astrophysical jets: scaled experiments and numerical simulations

“…It is, therefore, extremely interesting for us to be able to generate and study in the laboratory jets with Mach numbers and jet-to-ambient density ratios that are close to the ones inferred for YSO jets. It is worth noticing that, while the absolute velocities of the plasma jets produced in Z-pinch machines are fairly close to the velocity of the actual YSO jets, ∼200 km s −1 , they have densities that exceed the ambient density by orders of magnitude, typically jet electron density ∼5 × 10 18 cm −3 propagating in a vacuum (Lebedev et al 2004).…”

Distinguishing Propagation vs. Launch Physics of Astrophysical Jets and the Role of Experiments

“…The Lebedev et al (2002Lebedev et al ( , 2004 experiments show Mach number ≥ 15 jets. Jet deflection and shock propagation are studied in Lebedev et al (2004) experiments, where an additional cross-wind is introduced into across the propagating jet flow.…”

“…Once the current is driven, this lower inclination implies an increased density on the axis of the jet compared to Lebedev (2005), thereby increasing cooling enough to break the flux freezing. Lebedev et al (2002Lebedev et al ( , 2004 are thus supersonic hydrodynamic jet experiments. Given the discussion of Sec.…”

“…Jet deflection and shock propagation are studied in Lebedev et al (2004) experiments, where an additional cross-wind is introduced into across the propagating jet flow. Generally, the hydrodynamic cooling-collimated jets seem to be relatively stable to non-axisymmetric perturbations.…”

Astrophysics in 2005

“…Widgets designed for use in the laboratory have made or imitated (a) aurorae (Pedersen & Gerken 2005), (b) HerbigHaro objects (Lebedev et al 2004) and other sorts of magnetic jets (Lebedev et al 2005), and (c) grain alignments analogous to the Davis-Greenstein alignment of interstellar grains. Abbas et al (2004) used micron-sized non-spherical grains illuminated by lasers and rotating at 1-22 kHz.…”